Abstract
We tested 190 Klebsiella pneumoniae bloodstream isolates recovered from 189 patients in 30 U.S. hospitals in 23 states to determine the occurrence of extended-spectrum β-lactamase (ESBL) and AmpC β-lactamase producers. Based on growth inhibition by clavulanic acid by disk and MIC test methods, 18 (9.5%) of the isolates produced ESBLs. Although the disk diffusion method with standard breakpoints identified 28 cefoxitin-nonsusceptible isolates, only 5 (18%) of these were confirmed as AmpC producers. Of two AmpC confirmatory tests, the three-dimensional extract test was easier to perform than was the double-disk approximation test using a novel inhibitor, Syn2190. Three of the five AmpC producers carried the blaFOX-5 gene, while the other two isolates harbored the blaACT-1 gene. All AmpC genes were transferable. In vitro susceptibility testing with standard inocula showed that all five AmpC-producing strains were susceptible to cefepime, imipenem, and ertapenem but that with a high inoculum, more of these strains were susceptible to the carbapenems than to cefepime. All but 1 of 14 screen-positive AmpC nonproducers (and ESBL nonproducers) were susceptible to ceftriaxone and cefepime at the standard inoculum as were 6 of 6 isolates that were randomly selected and tested with a high inoculum. These results indicate that (i) a significant number of K. pneumoniae bloodstream isolates harbor ESBL or AmpC Β-lactamases, (ii) confirmatory tests are necessary to identify true AmpC producers, and (iii) in vitro, carbapenems are active against AmpC-producing strains of K. pneumoniae.
| Original language | English |
|---|---|
| Pages (from-to) | 772-777 |
| Number of pages | 6 |
| Journal | Journal of Clinical Microbiology |
| Volume | 41 |
| Issue number | 2 |
| DOIs | |
| State | Published - Feb 1 2003 |
Fingerprint
All Science Journal Classification (ASJC) codes
- Microbiology
- Microbiology (medical)
Cite this
Occurrence of extended-spectrum and ampC beta-lactamases in bloodstream isolates of Klebsiella pneumoniae : Isolates harbor plasmid-mediated FOX-5 and ACT-1 AmpC beta-lactamases. / Coudron, Philip E.; Hanson, Nancy D.; Climo, Michael W.
In: Journal of Clinical Microbiology, Vol. 41, No. 2, 01.02.2003, p. 772-777.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Occurrence of extended-spectrum and ampC beta-lactamases in bloodstream isolates of Klebsiella pneumoniae
T2 - Isolates harbor plasmid-mediated FOX-5 and ACT-1 AmpC beta-lactamases
AU - Coudron, Philip E.
AU - Hanson, Nancy D.
AU - Climo, Michael W.
PY - 2003/2/1
Y1 - 2003/2/1
N2 - We tested 190 Klebsiella pneumoniae bloodstream isolates recovered from 189 patients in 30 U.S. hospitals in 23 states to determine the occurrence of extended-spectrum β-lactamase (ESBL) and AmpC β-lactamase producers. Based on growth inhibition by clavulanic acid by disk and MIC test methods, 18 (9.5%) of the isolates produced ESBLs. Although the disk diffusion method with standard breakpoints identified 28 cefoxitin-nonsusceptible isolates, only 5 (18%) of these were confirmed as AmpC producers. Of two AmpC confirmatory tests, the three-dimensional extract test was easier to perform than was the double-disk approximation test using a novel inhibitor, Syn2190. Three of the five AmpC producers carried the blaFOX-5 gene, while the other two isolates harbored the blaACT-1 gene. All AmpC genes were transferable. In vitro susceptibility testing with standard inocula showed that all five AmpC-producing strains were susceptible to cefepime, imipenem, and ertapenem but that with a high inoculum, more of these strains were susceptible to the carbapenems than to cefepime. All but 1 of 14 screen-positive AmpC nonproducers (and ESBL nonproducers) were susceptible to ceftriaxone and cefepime at the standard inoculum as were 6 of 6 isolates that were randomly selected and tested with a high inoculum. These results indicate that (i) a significant number of K. pneumoniae bloodstream isolates harbor ESBL or AmpC Β-lactamases, (ii) confirmatory tests are necessary to identify true AmpC producers, and (iii) in vitro, carbapenems are active against AmpC-producing strains of K. pneumoniae.
AB - We tested 190 Klebsiella pneumoniae bloodstream isolates recovered from 189 patients in 30 U.S. hospitals in 23 states to determine the occurrence of extended-spectrum β-lactamase (ESBL) and AmpC β-lactamase producers. Based on growth inhibition by clavulanic acid by disk and MIC test methods, 18 (9.5%) of the isolates produced ESBLs. Although the disk diffusion method with standard breakpoints identified 28 cefoxitin-nonsusceptible isolates, only 5 (18%) of these were confirmed as AmpC producers. Of two AmpC confirmatory tests, the three-dimensional extract test was easier to perform than was the double-disk approximation test using a novel inhibitor, Syn2190. Three of the five AmpC producers carried the blaFOX-5 gene, while the other two isolates harbored the blaACT-1 gene. All AmpC genes were transferable. In vitro susceptibility testing with standard inocula showed that all five AmpC-producing strains were susceptible to cefepime, imipenem, and ertapenem but that with a high inoculum, more of these strains were susceptible to the carbapenems than to cefepime. All but 1 of 14 screen-positive AmpC nonproducers (and ESBL nonproducers) were susceptible to ceftriaxone and cefepime at the standard inoculum as were 6 of 6 isolates that were randomly selected and tested with a high inoculum. These results indicate that (i) a significant number of K. pneumoniae bloodstream isolates harbor ESBL or AmpC Β-lactamases, (ii) confirmatory tests are necessary to identify true AmpC producers, and (iii) in vitro, carbapenems are active against AmpC-producing strains of K. pneumoniae.
UR - http://www.scopus.com/inward/record.url?scp=0037314305&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0037314305&partnerID=8YFLogxK
U2 - 10.1128/JCM.41.2.772-777.2003
DO - 10.1128/JCM.41.2.772-777.2003
M3 - Article
VL - 41
SP - 772
EP - 777
JO - Journal of Clinical Microbiology
JF - Journal of Clinical Microbiology
SN - 0095-1137
IS - 2
ER -